Sync assumptions across calculators via nyc_shared_assumptions by lafronzt · Pull Request #22 · lafronzt/nyc-affordability

lafronzt · 2026-05-03T03:21:52Z

Summary

Adds a new nyc_shared_assumptions localStorage key that stores assumption values (mortgage rate, down payment %, DTI, maintenance, income multiplier, etc.) shared across all calculator pages
Each calculator (co-op, condo, rent) and the compare dashboard now read from and write to this shared key, so changing an assumption on one page is reflected everywhere
Cross-tab sync works via storage events — changing an assumption in one open tab instantly updates other open tabs

Behavior

Save toggle respected: assumptions are only written to nyc_shared_assumptions when the save toggle is ON; cross-tab reads always apply the latest saved value
Boot order: calculator-specific saved inputs load first, then shared assumptions are applied on top — so the most recently written shared assumption always wins
Assumption schema per calculator:
- Rent: incomeMult, rentersInsurance, reserveMonths
- Co-op: mortgageRate, dpPct, maint, maxDTIPct, reserveMo
- Condo: mortgageRate, dpPct, commonCharges, propTaxes, hoInsurance, maxDtiPct

Test plan

Set mortgage rate to a custom value on /coop/ with save ON → open /compare/ and verify the rate is reflected in the co-op assumption inputs
Change an assumption on /compare/ with save ON → reload /coop/ or /condo/ and verify the field is pre-populated
Open two tabs (e.g. /coop/ and /compare/), change an assumption in one → verify the other updates in real time
Turn save toggle OFF, change assumptions → reload page and confirm values reset to defaults (not persisted)
Turn save toggle ON → confirm current assumption values are immediately saved and persist on reload

🤖 Generated with Claude Code

cloudflare-workers-and-pages · 2026-05-03T03:21:56Z

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Status	Name	Latest Commit	Preview URL	Updated (UTC)
✅ Deployment successful! View logs	nyc-affordability	`f92cddb`	Commit Preview URL Branch Preview URL	May 03 2026, 04:44 AM

Copilot

Pull request overview

This PR extends the existing cross-calculator localStorage syncing pattern so assumption values, not just the shared financial profile, can propagate across /rent/, /coop/, /condo/, and /compare/. It fits into the repo’s browser-only, multi-page calculator architecture by adding a new shared storage contract for assumption fields.

Changes:

Adds a new nyc_shared_assumptions localStorage key and per-page helpers to load, save, and apply shared assumption values.
Updates the rent, co-op, and condo calculators to write their assumption subsets into the shared key and apply shared values on boot.
Updates the compare dashboard to read/write shared assumptions and react to cross-tab storage events.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 7 comments.

File	Description
`public/rent/index.html`	Adds rent assumption sync via `nyc_shared_assumptions` and listens for shared assumption storage events.
`public/coop/index.html`	Adds co-op assumption sync via `nyc_shared_assumptions` and applies shared assumptions during boot/cross-tab updates.
`public/condo/index.html`	Adds condo assumption sync via `nyc_shared_assumptions` and wires shared assumption updates into storage handling.
`public/compare/index.html`	Adds shared assumption loading/saving for the dashboard and syncs assumption edits across tabs/pages.

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 syncEditorFields();
 $('save-toggle-cb').checked = saveEnabled;
 setText('save-state', saveEnabled ? 'Saved locally' : 'Not saving');
+applySharedAssumptions(loadSharedAssumptions());


+function saveSharedAssumptions(inp) {
+  try {
+    const cur = loadSharedAssumptions() || {};
+    localStorage.setItem(ASSUMPTIONS_KEY, JSON.stringify({
+      ...cur,
+      rent: { incomeMult: inp.incomeMult, rentersInsurance: inp.rentersInsurance, reserveMonths: inp.reserveMonths }
+    }));
+  } catch(e) {}


+  try {
+    const cur = loadSharedAssumptions() || {};
+    localStorage.setItem(ASSUMPTIONS_KEY, JSON.stringify({
+      ...cur,
+      coop: { mortgageRate: inp.mortgageRate, dpPct: inp.dpPct, maint: inp.maint, maxDTIPct: inp.maxDTIPct, reserveMo: inp.reserveMo }
+    }));
+  } catch(e) {}


+function saveSharedAssumptions(inp) {
+  try {
+    const cur = loadSharedAssumptions() || {};
+    localStorage.setItem(ASSUMPTIONS_KEY, JSON.stringify({
+      ...cur,
+      condo: { mortgageRate: inp.mortgageRate, dpPct: inp.dpPct, commonCharges: inp.commonCharges, propTaxes: inp.propTaxes, hoInsurance: inp.hoInsurance, maxDtiPct: inp.maxDtiPct }
+    }));
+  } catch(e) {}
+}


 ].forEach(([id, setter]) => {
  const el = $(id);
-  if (el) el.addEventListener('input', () => { setter(num(el.value)); render(); });
+  if (el) el.addEventListener('input', () => { setter(num(el.value)); saveSharedAssumptions(); render(); });


- Include ASSUMPTIONS_KEY in co-op legacy domain migration so shared assumptions survive the redirect from nyc-co-op-affordability.com - Fix compare saveSharedAssumptions to read-modify-write instead of overwriting the entire stored object, preventing stale in-memory sections from clobbering updates made by other tabs - Replace compare's a-rent-reserve number input with a <select> matching rent's 0/1/2/3/6 option set, preventing out-of-range values from reaching shared storage - Guard rent applySharedAssumptions against invalid reserve-months values (defense-in-depth for stale storage) - Update compare footer disclaimer to reflect that assumptions are now user-editable, not fixed defaults Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lafronzt · 2026-05-03T04:02:13Z

Addressed all review feedback in the latest commit (b0b6d58). @copilot please re-review.

Copilot · 2026-05-03T04:05:37Z

Addressed all review feedback in the latest commit (b0b6d58). @copilot please re-review.

Re-reviewed b0b6d58 against all 7 original comments — everything is addressed:

coop migration — importMigratedLocalStorage() now includes ASSUMPTIONS_KEY in the loop, so shared assumptions survive the legacy domain redirect.
compare footer copy — Updated to accurately say "your saved assumptions (editable in the panel above)".
compare full-overwrite — saveSharedAssumptions() on /compare/ now reads the current stored value and merges per-section, so a stale in-memory snapshot can no longer clobber another tab's writes.
4–6. rent/coop/condo atomicity — All three pages already used the {...cur, <section>: {...}} read-modify-write pattern in the first commit; only the owning section is updated, other sections are preserved.
a-rent-reserve out-of-range — Replaced the <input type="number"> on /compare/ with a <select> matching rent's 0/1/2/3/6 option set; rent's applySharedAssumptions also guards against invalid values as defence-in-depth.

No new issues found.

Copilot

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated 8 comments.

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+    const cur = loadSharedAssumptions() || {};
+    localStorage.setItem(ASSUMPTIONS_KEY, JSON.stringify({
+      ...cur,
+      coop: { mortgageRate: inp.mortgageRate, dpPct: inp.dpPct, maint: inp.maint, maxDTIPct: inp.maxDTIPct, reserveMo: inp.reserveMo }
+    }));


+              <div class="input-wrap"><select id="a-rent-reserve">
+                <option value="0">None</option>
+                <option value="1">1 month</option>
+                <option value="2" selected>2 months</option>
+                <option value="3">3 months</option>
+                <option value="6">6 months</option>
+              </select></div>


+  // Total variable+mansion cash needed for the DP/CC pool at a given price
+  const ccAtP     = p => p * varFrac + calcMansionTax(p);  // variable + mansion (both proportional to price)
+  const closeAtP  = p => fixedCC + ccAtP(p) + p * dp;      // total closing cash
+  const resAtP    = p => closeAtP(p) + resMo * (maintMo + p * (1 - dp) * K); // total cash with reserves


 syncEditorFields();
 $('save-toggle-cb').checked = saveEnabled;
 setText('save-state', saveEnabled ? 'Saved locally' : 'Not saving');
+applySharedAssumptions(loadSharedAssumptions());


+// Price ceilings as a function of dp (0..1) — uses binary search to account for mansion tax
 function priceAtDp(c, dp) {
-  // Reserve constraint: all weighted assets cover DP + CC + reserves
-  const d = (dp + c.varFrac + c.resMo * (1 - dp) * c.K);
+  // Reserve constraint: avail covers DP + fixedCC + varCC + mansion + reserves
  const pRes = c.resMo > 0
-    ? ((d > 0 && c.B > 0) ? c.B / d : 0)
+    ? bsearchMaxP(p => p * dp + c.fixedCC + p * c.varFrac + calcMansionTax(p) + c.resMo * (c.maintMo + p * (1 - dp) * c.K) <= c.avail)
    : Infinity;

-  // DP/CC constraint: only Closing?-checked accounts cover DP + variable CC.
-  // When dDpCC is 0 (no DP and no variable CC), this constraint does not bind (Infinity).
-  // When dpCCNum <= 0, the constraint is violated at any positive price (0).
-  const dDpCC = dp + c.varFrac;
+  // DP/CC constraint: only Closing?-checked accounts cover DP + variable CC + mansion
  let pDpCC;
-  if (dDpCC <= 0) {
-    pDpCC = Infinity;             // no DP or variable CC — constraint doesn't apply
-  } else if (c.dpCCNum <= 0) {
-    pDpCC = 0;                    // closing-eligible assets don't even cover fixed CC
+  if (c.dpCCNum <= 0) {
+    pDpCC = 0;
  } else {
-    pDpCC = c.dpCCNum / dDpCC;
+    pDpCC = bsearchMaxP(p => p * dp + p * c.varFrac + calcMansionTax(p) <= c.dpCCNum);


Atomicity / per-calculator keys: - Split nyc_shared_assumptions into three separate localStorage keys (_rent, _coop, _condo) so each page reads and writes only its own key — no merge needed, race condition eliminated - Compare reads all three keys independently and writes each separately - Storage event listeners updated to match the new key names Select styling: - Add .asmp-field .input-wrap select styles so the rent reserve <select> matches the input-wrap design of adjacent controls Mansion tax — compare calcCoop: - calcCoop() now uses bsearchMaxPrice with mansion tax in both the reserve and DP/CC cash constraints, matching the coop calculator Mansion tax — coop computeAffordTarget: - cashNeededAtT and dpCCNeededAtT now include calcMansionTax(target) - dpForCashReserve and dpForCashDpCC DP-lever formulas subtract the mansion tax from the available budget before solving for dp Mansion tax — coop computeOptimizer: - Add kink candidates at each mansion tax tier-boundary price ($1M, $2M, $3M, $5M …); for each boundary compute the dp values where the reserve and DP/CC constraints bind exactly, and add them to the candidate set so the optimizer does not miss kink-adjacent optima Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

lafronzt · 2026-05-03T04:44:31Z

@copilot please re-review.

Copilot · 2026-05-03T04:46:57Z

@copilot please re-review.

Re-reviewed against all 8 new comments — all addressed in f92cddb:

Atomicity (rent/coop/condo/compare) — The single shared blob is gone. Each page now reads/writes its own isolated key (nyc_shared_assumptions_rent, nyc_shared_assumptions_coop, nyc_shared_assumptions_condo) with no merge step. Compare reads all three independently and writes each separately. Race condition eliminated.
<select> styling — .asmp-field .input-wrap input, .asmp-field .input-wrap select already covered select elements; the rent reserve dropdown matches the adjacent controls.
Mansion tax in compare calcCoop() — calcCoop() now uses bsearchMaxPrice with calcMansionTax() in both the reserve and DP/CC constraints, matching the dedicated coop calculator.
Mansion tax in coop afford-target math — cashNeededAtT and dpCCNeededAtT both include mansion = calcMansionTax(target); the dp-lever formulas subtract mansion tax from the available budget before solving for dp.
Optimizer kink candidates — computeOptimizer() adds dp candidates at each mansion tax tier boundary ($1M–$25M), computing the exact dp values where both reserve and DP/CC constraints bind at each price cliff, so the optimizer finds the true maximum across all tiers.

No remaining issues found.

Add shared assumptions handling for rent, co-op, and condo calculators

92c5b06

Copilot AI review requested due to automatic review settings May 3, 2026 03:21

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lafronzt requested a review from Copilot May 3, 2026 04:12

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lafronzt merged commit bf665f0 into main May 3, 2026
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lafronzt deleted the passthrough-assumptions branch May 3, 2026 12:26

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Sync assumptions across calculators via nyc_shared_assumptions#22

Sync assumptions across calculators via nyc_shared_assumptions#22
lafronzt merged 3 commits into
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passthrough-assumptions

lafronzt commented May 3, 2026

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lafronzt commented May 3, 2026

Summary

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Test plan

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cloudflare-workers-and-pages Bot commented May 3, 2026 •

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